A wide variety of additives are used in lubricating oils, greases and hydraulic fluids to improve their properties and enhance their performance. Additives can improve the performance of lubricating oils, greases and hydraulic fluids with respect to oxidation, wear and corrosion. One important property is oxidative stability. Antioxidants slow oxidative degradation by retarding or inhibiting a variety of degradation chemistries, thereby protecting and extending the life of formulated oils. Antioxidancy is described as the ability of an additive to delay the onset of oxidation by effectively quenching radicals that are generated by a system.
Many conventional antioxidants are stoichiometrically consumed in the degradation process. That is, conventional antioxidants are consumed in neutralizing a variety of degradation chemistries. More effective antioxidants are catalytic antioxidants. Catalytic antioxidants extend the useful life of formulated lubricants and may be used in significantly reduced concentration while maintaining good performance levels.
It would be desirable, therefore, to provide lubricating compositions and hydraulic fluids with antioxidants that perform more like catalysts in their antioxidation function, thereby enhancing the performance and extending the life of such lubricants and fluids.
Furthermore, it would be of great industrial interest to develop a process in which antioxidants that perform more like catalysts in their antioxidation function could be prepared from generally available starting compounds that are relatively inexpensive, available in commercially scale amounts and that are safe to handle.